Superabsorbent polymers (SAPs) are synthetic polymers that are able to absorb about 500 to 1000 times their own weight in water. Such superabsorbent polymers have begun to be used in real-world applications for sanitary items, and are currently being widely utilized not only in hygiene products, such as disposable baby diapers and the like, but also in gardening soil repair agents, water stop materials for civil construction, seeding sheets, freshness retaining agents in the field of food distribution, and fomentation materials.
In the preparation of the superabsorbent polymer, water, which is a polymerization medium, is used in various applications, including facilitating the dispersion of the crosslinking solution during the surface crosslinking process, etc. Also, residual moisture in the final product functions as an anti-static agent and a plasticizer for resin, and plays a role in suppressing the generation of very small superabsorbent polymer dust in the course of application and also preventing the grinding of the superabsorbent polymer particles. Generally, however, when water is added to the superabsorbent polymer, the surface stickiness of the polymer may be increased by the water absorbed thereto, and irreversible agglomeration of the superabsorbent polymer particles may take place. This increase in stickiness and agglomeration may result in poor processability, imposing a burden on the preparation and application processes, consequently increasing the particle size of the superabsorbent polymer, deteriorating the properties thereof, and decreasing productivity.
In this regard, Korean Patent Application Publication No. 2012-0081113 discloses a method of preparing an absorbent polymer containing water-insoluble inorganic particles. However, this conventional technique is problematic because the surface stickiness of the superabsorbent polymer increases with an increase in moisture content on the surface thereof, undesirably incurring agglomeration, poor processability, and low productivity, as mentioned above. Hence, there is required to develop superabsorbent polymers, which may satisfy both high moisture content and high processability.
In order to satisfy both high moisture content and high processability, porous superhydrophobic particles in ultrafine powder form may be used. Porous superhydrophobic particles in powder form have a very low bulk density of about 0.04 to 0.10 g/cm3, and thus the volume relative to the weight thereof is quite large, undesirably increasing transport costs and the space necessary for storage. Furthermore, it is not easy to add such particles in fixed amounts upon mass production and the likelihood of scattering the particles in the air is high, undesirably deteriorating workability and endangering the health of workers.
Accordingly, there is a need for superabsorbent polymers containing microparticles that have both high moisture content and high processability and are available in a liquid phase so as to facilitate the handling thereof, thereby increasing economic efficiency and workability.